Method of making induction heater ring



May 12, 1970 5. 1.. MOFARLAND 3 METHOD OF MAKING INDUCTION HEATER RINGFiled June 5, 1968 INVENTOR. GEORGE L. Mc FARLAND United States Patent O3,510,938 METHOD OF MAKING INDUCTION HEATER RING George L. McFarland,Salem, Va., assignor to General Electric Company, a corporation of NewYork Filed June 3, 1968, Ser. No. 733,924 Int. Cl. H01f 17/00 US. Cl.29602 2 Claims ABSTRACT OF THE DISCLOSURE A strip of chrome copper, orsimilar metal, formed into a circular shaped, partial ring with the endsof the strip separated and abutting each other, the ends of the stripalso being plated with silver, or other precious metal, whereby forceexerted across the perimeter of the device closes the ring bringing theends of the strip into intimate electrical contact so that the completedring may be used as a supplemental heating, internal short-circuitedsecondary, in an induction heater roll.

BACKGROUND OF THE INVENTION This invention is related to A.S.N. 731,952filed May 24, 1968, now abandoned and is assigned to the same assignee.

In this earlier application there is disclosed and claimed a roll type,induction heater essentially comprising a hollow cylinder havingconcentric rings in mutual contact with the inside of the cylinder atpreselected locations along the length of the cylinder for supplementingby induced eddy currents the heating of the cylinder to providepredetermined heating profiles according to the positions of theinternal rings. The rings referred to in the aforesaid earlierapplication are made from solid, hollow cylindrical stock, requiringconsiderable machining time and expense. It has been found that ringsformed from strips having their ends joined as taught in the presentinvention are equally effective and cheaper to manufacture.

SUMMARY OF THE INVENTION This invention relates to a ring formed from alinear strip of conductive metal of uniform cross section, the length ofthe strip being substantially equal to the desired circumference of thering. The strip is first formed partially into circular shape with theends of the strip separated and abutting, the ends thereafter beingplated, or otherwise covered with a layer of precious metal, so thatwhen they are forced together to complete formation of the ring reliableelectrical continuity is obtained throughout the circumference of thering.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a stripof conductive metal from which a circular ring is to be formed accordingto the invention.

FIG. 2 is a perspective view of a partially formed ring derived from thestrip shown in FIG. 1.

FIG. 3 is a perspective view of the completed ring that is shownpartially formed in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIGS. 1 and 2a strip composed of a conductive metal such as copper, brass-preferablychrome copper-is formed into a circular shape 13 (see FIG. 2) having itsends 11 and 12 adjacent each other.

For example, with a four inch diameter ring the gap between the ends 11and 12 may be approximately one inch. The ends of the strip arethereafter plated with a precious metal such as silver. If the ring isnot immediately installed into an induction heater roll, as described inthe earlier application referred to above, the ends are thereafterdipped in wax to preserve the precious metal from deterioration.

In applying the utility of the present invention to an induction heaterroll, as previously explained brieflly, the circular shaped, open endedring 13 of FIG. 2 is contracted by applying force across its perimeterto complete a closed ring 13a as shown in FIG. 3, the ends 11 and 12meeting at a common position 14. The ring 13a is thereafter forced intoa hollow cylindrical heater roll 16 having an inside diameter '17slightly less than the perimeter of the ring 13a. It is to be noted thata notch 15 is cut into the strip 10 prior to its being formed, thisnotch being useful in removing a ring 13a from a heater roll 16 when thering is to be changed or replaced. Before completing the formation ofthe ring, if the ends of the strip have been coated with wax, thisshould be removed by a suitable solvent.

It is to be noted that in the formation of rings as described above itis necessary that the plating of the ends of the strip be accomplishedafter the strip is formed into a circular shape. Otherwise it has beenfound that the forming rolls may damage the precious metal layers onthese ends.

It has been found that rings constructed according to the above afterbeing used in heater rolls to provide auxiliary induction heating of theroll are affected in a manner whereby the pressure of the ends incontact at the time of fitting into the heater roll, together with theheating incidental to use as a short-circuited secondary winding of theinduction heater and the eddy currents induced therein, produce abonding of the silver plated ends similar to, but stronger than, a coldweld.

While the invention has been explained and described with the aid ofparticular embodiments thereof, it will be understood that the inventionis not limited thereby and that many modifications retaining andutilizing the spirit thereof wihout departing essentially therefrom willoccur to those skilled in the art in applying the invention to specificoperating environments and conditions. It is therefore contemplated bythe appended claims to cover all such modifications as fall within thescope and spirit of the invention.

I claim:

1. The method of forming a conductive ring comprising cutting a strip ofconductive metal substantially equal in length to the circumference ofthe desired ring, forming the said strip into a partial ring with theends adjacent one another, placing a layer of precious metal upon eachsaid end, and applying force across the perimeter of said ring to closethe ends into intimate contact with each other.

2. The method set forth in claim 1 wherein the precious metal layer isplated upon the said ends.

References Cited UNITED STATES PATENTS 92,258 7/ 1869 Brooks 29492403,707 5/1889 Thomson 219-- 653,901 7/1900 Bray 29l83.5

1,486,479 3/1924 Bottiger 29-477 (Other references on following page)UNITED STATES PATENTS OTHER REFERENCES Ronci. Brady: Materials Handbook,McGraw-Hill, New York Bundy 29-492 (1966), p. 188.

Niven 29199 Bartlett 336-73 5 E. A. GOLDBERG, Primary Examiner Swarm us.01. X.R.

Reeve Pedlow 219-1053 X

